U.S. Pat. No. 3,517,534 describes an apparatus for producing tubes. According to the aforementioned patent, a tubular blank is placed around a mandrel and is clamped in a chuck at one end. A series of circumferentially spaced rollers are moved radially into engagement with the outer surface of the tubular blank while the mandrel and blank are rotated, and at the same time the rollers are moved axially along the blank. This results in the blank being subjected to both radial and axial deforming pressures through the rollers to thereby cause the metal of the tubular blank to flow axially ahead of the rollers to reduce the wall thickness of the blank.
The structure of the aforementioned patent can be used to obtain precision, high pressure tubing with smaller tolerances than standard mill drawn tubing in diameters ranging from 3 inches up to 10 inches, and this is accomplished by "spin forging" with no metal removal from the metal tubular blank.
However, certain difficulties have arisen in the past when attempting to spin forge larger diameter thin wall tubing, due to the problem of rippling on the internal diameter of the tube.